FDA Panel to Review Abbott's
XIENCE™ V
Drug-Eluting Stent
November 29 Meeting Follows Last
Month's
Recommendation of
Medtronic's Endeavor® Drug-Eluting Stent;
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November 5, 2007 -- Abbott
announced this morning that the U.S.
Food and Drug Administration (FDA) has confirmed a Circulatory Systems Devices
Advisory Panel meeting on November 29, 2007, to review the company's Premarket
Approval (PMA) submission for the XIENCE™ V Everolimus Eluting Coronary
Stent
System.
The PMA was filed on June 1, 2007.
While the FDA is not obligated to follow
the recommendations of its Advisory Panels, the agency usually
does so. Such
a review for Abbott's stent has been a topic of speculation
in the interventional cardiology community for some time, especially
on the heels of the same
Panel's
review
and unanimous
recommendation last month
of
Medtronic's Endeavor® drug-eluting stent.
Currently the only FDA-approved drug-eluting
stents are the Cypher® from
Cordis, a division of Johnson & Johnson, and the Taxus®,
made by Boston Scientific. Both have been on the U.S. market since
2003 and 2004 respectively, so there is much anticipation about
two new second-generation drug-eluting stents becoming available.
Medtronic is hoping to launch Endeavor in the next few months;
Abbott says it anticipates launch in the first
half of 2008, pending FDA
approval.
Both
stents have been
available
in
Europe
for
some time: Medtronic's Endeavor received the European CE Mark
approval in 2005; Abbott's Xience V became available in Europe
a little over a year ago.
Both newer stents make use of "imus" drugs,
relatives of sirolimus, the immunosuppressant drug used on the Cypher
stent. Abbott is using
everolimus and Medtronic's choice is zotarolimus or ABT-578, oddly
enough a
drug
manufactured by Abbott. To further blur company lines, Abbott's Xience
V stent is also sold by Boston Scientific, under the name "Promus" --
this co-marketing arrangement was part of the January 2006 Guidant
acquisition agreement made between the companies.
Without question,
the introduction of two new stents will increase the number of
players in what has been a shrinking market for drug-eluting stents
-- down
over a billion dollars worldwide, due to questions about safety
and the issue of late stent thrombosis, as well as disputes over
whether
the newer drug-eluting stents are really worth the cost, whether
the difference in performance when compared with bare-metal stents
is really as great as originally thought. Both Medtronic and Abbott
have emphasized these issues of safety and efficacy in their
submissions to the FDA.
Endeavor's Late Loss and Long
Term Data
While randomized clinical
trial outcomes
for the Endeavor show a
slightly
higher
amount of "late
loss" than
the rival Taxus stent, many physicians feel this is not necessarily
a problem. Late loss is the amount of tissue regrowth inside the
stent and subsequent reduction in diameter. At a
symposium last month, sponsored by Medtronic during the TCT meeting,
it was
shown that below a certain threshold
level, one that the Endeavor is well under, late
loss does
not
seem to translate to an increase in clinical events, such as the
need for repeat procedures, heart attack or death. In fact some
physicians
feel that "a little late loss is not a bad thing" and that
it may indicate improved healing, covering of the stent with healthy
endothelial
cells and a lower risk of late stent thrombosis. Indeed, the safety
profile of the Endeavor has borne this out and one
feature of the Medtronic submission that the FDA panel liked was
the large number of patients enrolled in the Endeavor studies (over
2,000) and the long-term followup (2 and 3 year data were available).
Low numbers and lack of followup in early drug-eluting
stent trials (Cypher and Taxus) were key criticisms made during
the FDA December stent safety panel hearings
Abbott's Superior Results Against Taxus
Abbott comes to the FDA Panel with somewhat shorter followup (out
to 2 years) and smaller total numbers of patients enrolled than
Medtronic's Endeavor, but with data showing significant superiority
to the market leader: Boston Scientific's Taxus stent. For those
who think late loss is in fact an indicator,
Abbott's
Xience V showed a 50% reduction in late loss
over Taxus at 8 months. Additionally, and impressive to many, Abbott
reported that XIENCE V demonstrated clinical superiority to TAXUS
with a
significant
43
percent reduction in Major Adverse Cardiac Events (MACE) compared
to TAXUS at one year -- their PMA submission to the FDA is the
first one to show that a drug-eluting stent is superior in these
areas to the current market leading device.
As these newer stents make their way to market,
research has been ongoing into newer devices. One promising idea
that has generated much excitement with its early results is the
bioabsorable stent. Both Abbott and German manufacturer Biotronik
have been working on stents that will hold open the artery after
balloon angioplasty, deliver a dose of drugs to keep blockages from
growing back, and then after six months or so will
be reabsorbed into the body, leaving no trace.
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